Others use more general principles derived from physics-based dimensional scaling analysis of ideal motor models.
Under a mass constraint and some given torque requirement, maximizing motor gap radius \(r_g\)  is often considered the best way to address the design priorities established above [1]}, [2]}, [3]}, [4]}.
The following are developed in [1]}, reproduced with minor nomenclature adjustments:
\(K_T &\propto r_g^2 l \\K_T/m &\propto r_g \\K_T/J_m &\propto 1/r_g \\K_M^2 &\propto r_g^3 l \\J_m &\propto r_g^3 l\) 
